[GeoMechanicsApplication] Extend ApplyCPhiReductionProcess to use Mohr-Coulomb constitutive model

[markelov208]

The C Phi reduction process has been created before GeoMechanicsApplication had an own Mohr Coulomb constitutive model.

As a user I would like to use the Mohr-Coulomb model and the C Phi reduction process shall be able to get its parameters from the Mohr Coulomb constitutive model.

The possible changes are

• add a reference on Mohr-Coulomb model,
• change GetAndCheckPhi GetAndCheckC accordingly in ApplyCPhiReductionProcess and change SetCPhiAtElement in ApplyCPhiReductionProcress
• Add unit tests

This issue is related to [GeoMechanicsApplication] Improve the error message for "GEO_SHEAR_CAPACITY" output

Remark 10/11/2025: This check of C-Phi needs to be moved to ConstitutiveLawUtilities. Later on, we can reuse this for output calculation, for instance shear capacity check.